Control Colorado Potato Beetle with a Mix of Strategies - Vegetable Gardener Control Colorado Potato Beetle with a Mix of Strategies Unchecked, the Colorado potato beetle can munch its way through your potato, eggplant, and tomato plants. courtesy U.S. Department of Agriculture Colorado potato beetle eggs are laid on the underside of leaves. Boyd Hagen Colorado potato beetle larva. Boyd Hagen Unchecked, the Colorado potato beetle can munch its way through your potato, eggplant, and tomato plants. Photo: courtesy U.S. Department of Agriculture April 2000 from issue #26 The pretty yellow-and-black-striped Colorado potato beetle is native to wild Solanaceous plants of the semi-arid western United States. Our problem with it began when the beetle broadened its gustatory interests to include cultivated plants in the same family, such as potato, eggplant, and tomato. It has since expanded its range to include most of North America and Europe. Because the Colorado potato beetle has become resistant to a large number of conventional pesticides, researchers have pursued alternative methods of control. As a kitchen gardener, you can choose from physical, horticultural, or biological controls. Most likely, a mix of strategies will be your best policy.

Rotation—the old standby In spring, adult Colorado potato beetles emerge from hibernation in the soil and search out food plants for feeding and egg-laying. The feeding beetles lay yellow-orange eggs clustered in groups, usually on the undersides of leaves. The larvae, which look like fat, globular, slow-moving caterpillars, change from brown to pink as they grow, developing two rows of black spots along each side of their abdomen (top right photo, below). When fully grown, in 20 to 24 days, the larvae burrow into the soil to pupate near the plants on which they were feeding. Emerging as adults, a week to two weeks later (depending on the temperature), they start the process again. The second generation of adults remains in the soil until the next spring. Colorado potato beetle eggs are laid on the underside of leaves. Fortunately, they're food to lady beetles. The yellow and black striped Colorado potato beetle overwinters near plantings it infested the previous year, so rotating crops may provide some protection against it. The adult beetles are poor flyers and cannot easily travel far.

For this reason, the rotation of crops away from where Solanaceous plants have been planted before is a traditional means of controlling Colorado potato beetle. Unfortunately for the kitchen gardener, the new plantings ideally should be at least 200 feet away from the old site. Even in small gardens, however, it’s still a good idea to rotate each piece of ground to a different plant family, because other pests, including soil-borne pathogens, remain behind from each year’s plantings. Handpick, vacuum, or trap Physical controls satisfy the urge for immediate revenge on a pest for the damage it causes, and against the Colorado potato beetle, you have several choices. Handpicking may be all you need to protect a small plot of potatoes. Picking is easiest early in the day when the beetles are cold and slow to move. Collect the beetles in a wide-mouth jar, coffee can, or deep baking pan, half full of soapy water. Place the container below leaves with beetles or larvae and shake the plant. The insects will fall into the container and drown. Larvae and egg masses also can be squished on the leaves. Gloves make the job easier. Another physical control option is to vacuum up the beetles.

Small, rechargeable hand-held vacuums can be quite effective with Colorado potato beetles and other large insect pests. We have also used a water vacuum, which sucks the beetles into a cylinder of soapy water, although its long power cord carries the danger of tripping us or decapitating a plant or two. To prevent the beetles from reaching early-sprouting tubers, especially in large plantings, you might want to dig a barrier ditch around your potato bed. The early colonizers walk to their first food sources. A near-vertical-sided, plastic-lined, dry ditch 4 to 6 inches deep and 4 inches wide cutting across their line of movement can trap these migrants and prevent early colonization. Timing and trap crops Planting dates turn out to be important for the control of Colorado potato beetle. A standard recommendation is to plant potatoes very early (early April in Ohio, for instance), so that the plants bloom before June, and the beetle damage occurs too late to affect yield. To advance the season, place plastic sheets on the soil to warm it up. Shifting planting dates at the other end is also a possibility. If your season length permits it, delay planting altogether until a month or more past May.

Another option is to plant an early potato crop as a trap crop. When the early crop is attacked, you can kill the beetles with a flamer. For a small garden, an ordinary hand-held propane torch will work as well as a long-handled weed flamer. Potato sprouts are fairly resistant to heat damage, and early sprouts attacked by the beetles will re-grow even if they’ve been damaged by fire. Or you can plant a main crop directly after flaming. Keep in mind that flaming cannot be used with a straw mulch or other inflammable mulch materials. Mulches and row covers Planting potatoes in, or just beneath, a thick straw mulch has been shown to reduce damage from a number of potato pests, including aphids and flea beetles, as well as Colorado potato beetles. Mulches attract predators, such as carabid ground beetles and hunting spiders, which feed at night. But mulches may not be successful in damp cold areas where slugs are a problem. As is the case with so many pest problems in small vegetable gardens, preventing migrating insects from reaching the plants by using row covers is a useful tactic.

Anchor the covers securely into the soil because Colorado potato beetles are strong walkers and could move in under unburied row cover edges. Nematodes and parasites The deliberate introduction of biological controls can be effective against the Colorado potato beetle. The cost of these predators and parasites may make it desirable for you to split the purchase with friends and neighbors. But releasing just one batch can help restore natural enemies of the beetles to areas depleted by years of spraying or habitat destruction. Before planting, you can introduce purchased beneficial nematodes into the beds. Be sure the soil is moist, and carefully follow the package instructions. We water in nematodes late in the day to prevent them from drying out before moving into the soil. The nematodes are most effective in light, well-drained soils, since they move within the soil and water solution. Heavy clay soils discourage their distribution below ground. Beneficial nematodes attack the overwintering beetles as they lie buried in the soil. They will help reduce flea beetle and click beetle larvae as well. The tiny parasitic mini-wasp Edovum puttleri is also commercially available.

Research has shown that it may parasitize up to 50 percent of the Colorado potato beetle egg masses on potatoes and an even higher percentage on eggplant (up to 91 percent). If you grow both potatoes and eggplant where Colorado potato beetle is a problem, you may find it worthwhile to release Edovum puttleri. Many garden catalogs include this species. Release the wasps when you see the first yellow egg masses. Release them again on the second batch of eggs in early summer. In many areas this second batch of eggs is the start of the heavy damage period. There are also a number of predatory insects that feed heavily on Colorado potato beetles. Soldier bugs are one such predator, and there is now a commercially available attractant to increase their numbers in the garden. At first glance, soldier bugs look like stink bugs, but by watching you may see them attack other insects. Among your vegetables, include plantings that bring in the natural predators and parasites of a wide variety of pests. Coriander, dill, fennel, and sweet alyssum will sustain many beneficial insects, including some that prey on Colorado potato beetles.

Insect diseases In general, a good way to reduce insect pest numbers is with a pathogen that causes disease in the insect, is specific to it, but does not kill its natural enemies. A number of new Btt (Bacillus thuringiensis tenebrionis) products have high selectivity for Colorado potato beetles and virtually no mammalian toxicity. Btt works best against the early larval stages, so must be timed properly. Wait until all the egg masses have hatched. You can tell because only the shells will be left, and little larvae will be crawling nearby. The larvae have to eat the Btt from the leaf, so coat the leaves thoroughly, especially the undersides. This Btt is different from the better-known Bt pathogen used to control caterpillars. Be careful to get the right product. Like all live biological products, Btt can be damaged by long storage and high heat, so purchase it from a reliable source. Follow the directions carefully, since mixing with soft water (low pH) is essential. The directions will tell you how to do this and what remedy to follow if your water is hard (i.e., it contains calcium and other minerals).

Beauveria bassiana is a commercially available fungal pathogen that is effective against Colorado potato beetles. Beauveria bassiana has a wider host range than Btt and works best under moist conditions. As with the Btt, it is most effective against the young larvae. However, it can also be sprayed directly on the beetles. With so many methods available for preventing intolerable damage, you can keep a few Colorado potato beetles in the garden as appreciated wildlife rather than as overwhelming pests. Colorado Potato Beetle Management | Entomology Colorado Potato Beetle Management ENTFACT-312: Colorado Potato Beetle Management | Download PDF Ric Bessin, Extension Entomologist University of Kentucky College of Agriculture Colorado Potato Beetle The common black and yellow-striped "potato bug", a very familiar insect to home gardeners, is the most serious insect pest of potatoes. Both the striped beetle and the black-spotted, red larva feed on potato leaves. Their damage can greatly reduce yield and even kill plants. In addition to potato, Colorado potato beetle can be a serious pest of tomato, eggplant, and pepper. The Colorado potato beetle is notorious for its ability to rapidly develop resistance to insecticides that are used repeatedly for control.

This has been a serious problem on the east coast for some time, and is becoming more of a problem in Kentucky. With a limited number of insecticides available, some homeowners feel they have exhausted their control options when it becomes resistant to one or more insecticides. Biology Colorado potato beetles overwinter in the soil as adults. They become active in the spring as temperatures rise and begin to feed on weeds and volunteer or early planted potatoes, even entering the soil to attack emerging foliage. Female beetles lay orange-yellow eggs in batches of about two dozen or so on the underside of the leaves. Each female can lay 500 or more eggs over a four to five week period. Eggs hatch in four to nine days and the larvae begin to feed on potato foliage. The larvae are humpbacked with two rows of black spots on each side. They usually feed in groups and damage can be severe. The larval stage lasts two to three weeks. CPB Larvae Full grown larvae burrow in the ground to pupate. In five to 10 days, the adult beetle emerges. This insect can go from egg to adult in as little as 21 days.

The newly emerged adult female feeds for a few days before egg laying begins. There are two full and occasionally a partial third generation each year. If foliar sprays are used, an effort should be made to treat just after most eggs have hatched but before serious plant damage occurs. Resistance Management Insecticides in the same chemical class usually have the same mode of action, the same method of killing the insect. Resistance develops more rapidly to an insecticide when that insecticide is used repeatedly as the only control measure. Repeated use of one class kills susceptible beetles, leaving those that are resistant. Overuse of one insecticide may favor the development of resistance to other insecticides in the same chemical class. Consequently, to delay or prevent resistance it is important to avoid repeated usage of one particular insecticide by rotating the insecticides used. Rotation needs to be among different classes of insecticides (see table below). For example, rotation between Warrior and Asana would not be as effective as a Platinum, Asana rotation. Because Warrior and Asana are in the same class of chemicals and have the same mode of action, little is gained with this type of rotation. Note that the insecticides marked with an asterisk in the table are available to homeowners.

Table 1. Availability of Insecticides to Control Colorado Potato Beetle on Different Crops Bacillius thuringiensis var tenebrionis (Bt) is effective against small larvae (less than 1/4 inch) and should be applied at egg hatch or when larvae are first seen. A premature treatment may lose much of its effectiveness before the eggs hatch. Larger larvae are more difficult to control with Bt. Azatin, an extract of the neem seed, prevents the larvae from developing normally. Frequently, control failures with Colorado potato beetle are due to other factors besides just insecticide resistance alone. Timing of sprays is critical for control. Overwintering beetles are attracted to fields over a period of several weeks; spraying an insecticide too early may only control a portion of those beetles. However, waiting until larvae are nearly full grown also increases the chances of control failure. Small larvae are much easier to control with an insecticide than large ones. Using the correct amount of insecticide as well as obtaining complete coverage of the plants is important. Insecticides should only be used when needed. Potato plants can withstand considerable defoliation without yield loss.

Plants can loss up to 30% of their foliage without yield loss. Generally, insecticides do not need to be applied unless there is more than an average of one beetle or larva per plant. Additionally, some beneficial insects such as birds, predatory stink bugs, and parasitic flies will help to reduce Colorado potato beetle numbers somewhat. Other non-chemical control measures such as hand picking of adult beetles and immature stages is encouraged as this will aid to delay the development of resistance. Hand picking can be particularly effective in reducing the numbers of overwintering beetles coming to the young plants in the spring. Resistance by Colorado potato beetles should be managed on a field to field basis. While they may be resistant to one insecticide in a particular location, those in other areas within the same county may not have developed resistance to that insecticide. Revised: 1/04 CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.

Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE! Photos courtesy Ric Bessin, University of Kentucky Entomology Categories: Planttalk Colorado - Flea beetles on vegetables 1446 Flea Beetles on Vegetables There are several flea beetle species in Colorado. These beetles commonly attack vegetable plants including tomatoes, potatoes, peppers, eggplant, cabbage, broccoli, beans, radishes, beets and lettuce. Adult flea beetles are small and shiny. When disturbed, they jump. The western cabbage flea beetle, pale-striped flea beetle and western potato flea beetle are the most damaging species. They eat small holes in leaves and, during heavy infestations, the plant's growth is greatly reduced and it may die. Flea beetles overwinter as adults under plant debris or weeds adjacent to the garden. The larvae are white and worm-like and are found on plant roots. Larvae cause little damage, except for the western potato flea beetle, which tunnels into tubers. There are usually one to two generations of beetles in a year. Use healthy, actively growing transplants and encourage their rapid establishment to prevent flea beetle attacks.

Floating row covers also can exclude flea beetles from the garden. When necessary, garden insecticides containing carbaryl (Sevin), spinosad, bifenthrin and permethrin can be used to control heavy infestations. For more information, see the following Colorado State University Extension fact sheet(s). HGIC 2215 Sweet Potato & Irish Potato Insects : Extension : Clemson University : South Carolina CU › Cooperative Extension › HGIC › Insects, Diseases & Other Problems › Insects & Diseases of Plants › Insects & Diseases of Vegetables & Fruits › HGIC 2215 Sweet Potato & Irish Potato Insects Sweet Potato & Irish Potato Insects Pesticides updated by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 10/16. Revised pesticides updated by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University 2/14. Originally prepared by Randall P. Griffin, Extension Entomologist, Clemson University. New 07/99. Revised Images added 05/09. HGIC 2215 Printer Friendly Version (PDF) Wireworms Several kinds of wireworms feed on sweet potatoes as well as Irish potatoes.

The southern potato wireworm (Conoderus falli) is injurious in the southeastern United States. Adults (click beetles) are dark brown, about ¼ inch long and are found near the soil surface under leaves and trash in sweet potato plantings. Adults do not feed on potato plants. Tobacco wireworm adult (Conoderus falli). Natasha Wright, Florida Department of Agriculture and Consumer Services, Eggs are laid in the soil from late spring to early fall. They hatch in five days during midsummer, but may take several weeks during cool weather in the spring or fall. Potatoes are injured by larvae (immature forms). The larvae are white, cream or yellowish-orange with reddish-brown heads and tails. They are smooth, shiny and relatively hard-bodied. When fully grown they are ½ to ¾ inch long. The larvae change to pupae (immature nonfeeding stage where larva changes to an adult) in earthen cells in the ground. One to two generations of this wireworm occur each year. Injury by wireworm larvae usually consists of fairly small irregularly shaped holes.

If growth cracks or other breaks in the skin are present, holes may be concentrated in these, otherwise the holes are scattered at random over the surface of the root. The original holes are usually less than a quarter of an inch deep but may be considerably deepened by later growth of the root. A good indicator of wireworms is new feeding holes with ragged edges, usually containing chewed root fiber. Wireworms usually attack potatoes late in the season. Consequently, they produce less "healed-hole" injury (early season injury that has been healed over). The tobacco wireworm (Conoderus vespertinus) also damages potatoes. Adults are similar in size and shape to those of the southern potato wireworm, except for areas of light and dark brown. The immature stages are also very similar. Tobacco wireworm larvae (Conoderus falli). R.J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company, Only one generation of the tobacco wireworm occurs each year. The eggs, which are laid during the summer, hatch into larvae in one to three weeks. Pupation takes place during the late spring and summer of the following year.

Most overwintered larvae have pupated before sweet potato roots begin to enlarge; therefore, injury is probably caused by larvae from eggs laid during the current year. Home gardeners can use various measures to control wireworms. Trap wireworms in pieces of potato scattered around the garden, rotate crops and plow or cultivate infested soil in late summer or in autumn to kill or expose various insect stages to predators. Cultivation in the spring, well in advance of planting can help reduce wireworm populations. The sweet potato varieties Nugget and All Gold possess some resistance. Cucumber Beetles Larvae of both the banded cucumber beetle (Diabrotica balteata) and the spotted cucumber beetle (Diabrotica undecimpunctata howardi) feed on the roots of the sweet potatoes. Banded cucumber beetle (Diabrotica balteata). Clemson University - USDA Cooperative Extension Slide Series, Injury to sweet potatoes by these beetles is identical. Eggs, larvae and pupae of the two species are also identical. Cucumber beetle larvae eat small, round holes through the skin of sweet potato roots and form irregularly shaped enlarged cavities just under the skin.

The larvae seldom tunnel into the roots, as do elongate flea beetle or striped flea beetle larvae. Feeding scars are usually in groups rather than scattered randomly over the root. Original holes are usually shallow but may be deepened by later growth of the root. In contrast to wireworms, cucumber beetles often attack sweet potatoes early in the season. This results in much healed-hole injury. Spotted cucumber beetle (Diabrotica undecimpunctata howardi). J.P. Michaud, Kansas State University, Handpicking to remove the beetles is time-consuming but effective. In addition, several predators and parasites are enemies of cucumber beetles. Eliminate weeds in and around the garden. Flea Beetles Both the elongate flea beetle (Systena elongata) and the palestriped flea beetle (Systena blanda) feed on sweet potatoes. The habits and life histories of the two species are similar, and the immature stages look alike. Palestriped flea beetle (Systena blanda). Whitney Cranshaw, Colorado State University, These insects have a wide range of hosts, including many weeds. Adults move into sweet potato fields during the spring and summer and lay creamy yellow eggs in the soil.

These hatch into white larvae, which are soft-bodied, and about ⅜ inch long when fully grown. They have brown heads and a fleshy pointed tubercle (small knob-like protuberance) on the tail end. The larvae mature in 20 to 30 days, and then curl up in a cell made in the soil and transform into pupae. Adults emerge in about one week. At least two generations occur per year in the south. Larvae eat small holes through the skin of sweet potatoes and make enlarged cavities and short tunnels just under the skin. Except for these tunnels, injury is very similar to that of cucumber beetle larvae, which seldom tunnel into the roots. At harvest time, early season injury usually appears as shallow, healed scars which tend to be long and irregularly shaped. Flea beetles often migrate in from weedy areas, so keep weeds controlled near the garden. Plant flea beetle tolerant sweet potato varieties, such as Centennial and Jewel. Sweet Potato Flea Beetle Sweet potato leaves are often damaged by sweet potato flea beetles (Chaetocnema confinis); however, most damage to the plant occurs from larvae feeding on the roots.

Adult beetles are black, about 1/16-inch long and usually hop away when disturbed. They are easily recognized by the tendency to eat narrow grooves in the upper surface of sweet potato leaves. Larvae make small winding tunnels just under the skin of sweet potato roots. These tunnels are nearly invisible at first but soon darken and can be seen through skin. As roots grow, the skin over the tunnels splits away, leaving shallow scars on the surface. Sweet potato varieties differ widely in their susceptibility to economic injury by this insect. This injury is only cosmetic, but may impact the marketability of the potatoes. Controlling weeds along borders of garden and plowing under crop debris destroys overwintering and egg laying sites. Plant resistant varieties, such as Jewel and Centennial. Grubs Grub injury to sweet potatoes occurs in most areas where the crop is grown. There are many species of grubs and several of them feed on sweet potatoes. Grubs are the larvae of May beetles (Cyclocephala species) or green June beetles (Cotinis nitida). Green June beetle larva (Cotinis nitida).

Clemson University - USDA Cooperative Extension Slide Series, Adults of the various grubs vary in size and color, but all are robust beetles. Green June beetle adult (Cotinis nitida). Natasha Wright, Florida Department of Agriculture and Consumer Services, Eggs are laid in the soil during the spring and summer and soon hatch into fleshy larvae that are typically C-shaped. They are usually white or cream with light-tan and grayish areas on the tail. Larvae pass the winter in the soil and change into pupae the following spring. Grubs carve broad shallow areas in sweet potato roots. Since grubs feed upside down in the soil, horizontal roots are injured mostly on the underside. Cultivate garden soil well in advance of planting, and hand collect grubs during raking and leveling of soil. Sweet Potato Weevil The sweet potato weevil (Cylas formicarius elegantulus) is a serious pest of sweet potatoes but occurs only in certain parts of South Carolina, mostly in the coastal counties. Sweet potato weevil adult (Cylas formicarius elegantulus). Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Adult sweet potato weevils are ant-like beetles about ¼-inch long.

The head and wing covers are metallic dark blue and the thorax (chest region) and legs are bright orange red. Adult weevils feed on the exposed part of the sweet potato plant but prefer the roots. Feeding scars on the roots consist of tiny shallow holes usually in patches. Eggs are laid in specially prepared cavities in the vines or roots. Egg cavities are similar to the feeding punctures but may be distinguished by a mucus covering secreted by the female. Eggs hatch in about a week during warm weather. Larvae are white to ivory with light brown heads. When fully grown in two or three weeks, they are about 3/8-inch long. Pupae are found in the vines or roots. In a week or longer they change into adult weevils. As many as six or eight generations may be produced in a year. Injury to sweet potatoes by weevil larvae can be recognized by tunnels that start just beneath the skin and become larger as they extend inward. Adult exit holes are about the size of a match. When cultivating, throw soil around the base of the vines to prevent adult weevils from reaching the sweet potatoes underground.

Destroy all crop debris and culls at the end of the season, as well as volunteer sweet potato plants and morning glories (an alternate host plant) to eliminate breeding sites for weevils. Use crop rotation and plant tolerant sweet potato varieties, such as Centennial. Use of deep-rooted varieties, such as Porto Rico may help reduce damage. Potato Leafhopper The potato leafhopper (Empoasca fabae) is considered an important pest to Irish potatoes and is known to feed on nearly 200 other kinds of plants. Potato leafhopper adult (Empoasca fabae). Steve L. Brown, University of Georgia, Feeding by this leafhopper on potatoes causes curling, stunting and dwarfing, accompanied by a yellowing, browning or blighting of the foliage known as hopperburn or tipburn. The injection of saliva into the plant during feeding produces a physiological disturbance with disease-like manifestations. Symptoms are sometimes confused with drought stress. The adult is pale green, somewhat wedge-shaped, about ⅛ inch long, with small white spots on the head. Adults are very active, jumping or flying when disturbed. Females deposit slender white eggs within the stems and larger veins of the leaves.

Hatching occurs in six to nine days during the summer, and the pale green nymphs (immature forms that closely resemble the adult insect) molt five times before they become fully-grown and transform to winged adults. The period from egg to adult is about three weeks during warm weather; several overlapping generations develop each season. The potato leafhopper has not been found overwintering north of the Gulf States where it breeds throughout the year. Migration northward with the warm spring winds occurs annually. Colorado Potato Beetle Universally known among growers as the potato bug, the Colorado potato beetle (Leptinotarsa decemlineata) was long considered the most dangerous enemy of Irish potatoes. It is still capable of doing much damage and can be a serious pest of tomatoes or eggplants. The potato beetle is now found in most regions where potatoes are grown. Colorado potato beetle adult (Leptinotarsa decemlineata). C. Trouvé, Service de la Protection des Végétaux, Adults are stout, oval, convex beetles, about ⅜ inch long, with 10 black and yellow stripes running lengthwise along the wing covers.

Overwintering beetles hibernate in the soil, emerging in the spring about the time that potatoes come through the ground. They lay orange-yellow eggs in groups of a dozen or more on the undersides of the leaves. Each female deposits approximately 500 eggs over a five-week period. Eggs hatch in a few days and the dark red larvae devour the foliage, becoming orange as maturity approaches. There are two rows of conspicuous black dots on the sides of their bodies. When mature, they leave the plant, enter the soil and pupate, emerging as adults several days later. The life cycle requires about a month, and there are one to three generations per year. Injury is due to actual consumption of foliage and stems by adults and larvae, however, potato plants can lose up to 30% of their foliage without a loss of yield. Colorado potato beetle eggs (Leptinotarsa decemlineata). Whitney Cranshaw, Colorado State University, Over the years, it has become resistant to most pesticides and is a major potato pest. A 3- to 5-inch layer of straw added just before the potatoes emerged can lead to higher yields.

Soil temperatures will be cooler, soil moisture levels higher, and the populations of Colorado potato beetles will be lower in mulched gardens. Hand picking beetles and larvae, and removing leaves with egg clusters both can reduce the population significantly. The assassin bug is a beneficial predator that will help control the larvae of the Colorado potato beetle. Control of Potato & Sweet Potato Insects Keep over-wintering grass and broadleaf weeds controlled, as well as those during the growing season. The over-wintering weeds are often an initial source of insect pests on vegetables. Control warm-season weeds, especially morningglory near sweet potatoes, and solanaceous weeds, such as nightshade or horse nettle, near Irish potatoes. These weeds attract insect pests, which may move to feed upon the vegetable crops. Continually rotate where you plant root crops within the garden, and perform winter tilling to help keep soil insect pests in check. Encourage beneficial insects by planting a variety of herbs and flowers near the garden. Table 1 lists the natural and conventional contact insecticides for the control of insect pests of Irish and sweet potatoes.

However, limit the use of broad-spectrum contact insecticides, such as malathion, permethrin, carbaryl and pyrethrin, all of which kill beneficial predators and parasites of insect pests. Table 2 lists examples of available brands and products of natural and contact insecticides labeled for use on Irish and sweet potatoes. It also gives the pre-harvest interval (PHI) for each insecticide, which is the number of days to wait between insecticide application and harvest. Table 1. Insecticides for Control of Insect Pests of Irish Potatoes & Sweet Potatoes. Insect Pest University of Vermont A Publication of UVM Extension's Vermont Vegetable and Berry Program Colorado Potato Beetle Vegetable and Berry Specialist University of Vermont Extension Anyone who grows potatoes is familiar with the Colorado potato beetle. This insect pest is one of the best known beetles, famous for it’s ability to devour vegetables in the nightshade family: potato, tomato, eggplant and peppers. The adult beetles as well as their larvae can strip the plants of leaves and ruin an entire crop, if left to their own devices. The rather attractive dome-shaped adults are nearly a half-inch long, yellow, with five black stripes on each wing cover.

In late spring, after hibernating in the soil, usually along field edges, they emerge, with one thing on their mind: finding a food source. They walk toward this goal for a few days until they have the strength to fly about looking for potato plants or their relatives. Once they find them, the female beetles start snacking on foliage and laying clusters of 15 to 25 bright yellow-orange eggs on the undersides of the leaves. From these hatch the soft-bodied, hump-backed larvae that look a little like slugs. They larvae start out small but grow fast, molting four times into larger stages, or instars. The last instars grow to be quite plump, and they’re the ones that eat the most foliage. Then, they crawl into the soil and pupate. From this resting stage, a second generation of adults emerges by the end of the season, ready to eat again before passing the winter underground. It’s amazing that not long ago, this serious pest of vegetables pest was a harmless, well-behaved insect. It fed only on the buffalo bur, a tough weed that grows along the eastern foothills of the Rocky Mountains.

Then, about 150 years ago, the beetles discovered a new food growing in the white man's gardens. It adopted the cultivated potato as its favorite food, spread rapidly, and we’ve been fighting Colorado potato beetles ever since. It happened like this: with the opening up of the West following the Mormon migration to Utah in1847 and the California gold rush of 1849, pioneers arrived by the thousands and many of them planted potatoes. By 1855 potato growing reached westward to the native home of the beetle, and the insect started to spread eastward along the routes traveled by the pioneers. By hitchhiking and flying with the prevailing winds, the beetle migrated about 85 miles a year. It reached Nebraska in 1859, Illinois in 1864, Ohio in 1869, and the Atlantic coast in 1874. This caused great alarm overseas, and almost every European country banned the importation of American potatoes. Europe’s potato growing regions remained free of potato beetles until after World War One, when they appeared near Bordeaux, France, where there had been concentrations of American troops and supplies. Now the beetle is widespread in Europe, too.

Prior to the coming of the Colorado potato beetle as a pest, the name "potato bug" was used to describe a different beetle that is a relatively minor pest on potatoes. Now called the “old-fashioned potato bug”, this long slender beetle has two black stripes on each wing cover. The adult feeds on potatoes but lays its eggs in the ground and the predatory young feed on grasshopper eggs and the like. There are many naturally occurring controls of Colorado potato beetle. Fungi infect them, beneficial insects attack them, and toads and birds eat them. Rarely, however, do these forces combine to offer sufficient control to protect crops. Home gardeners resort to hand picking the beetles, followed by squishing, stomping or drowning them. Over the years, farmers have unleashed an arsenal of insecticides against the potato beetle, only to find it developed resistance to many of them. In recent years, new pesticide materials have been developed that have lower human toxicity and less environmental impact than those of the past. The most widely used of these is a strain of the B.t. bacterium that specializes in infecting potato beetles. It’s sold under several bio-insecticide brand names.

However, development of resistance remains a concern if a single class of insecticide is relied upon too heavily for control. Cultural practices play an important role in the management of Colorado potato beetle, as they help minimize the need for insecticides, protect natural predators, and prevent the development of pesticide resistance. Such practices include crop rotation, trapping, mulching, row covers, and flaming. By changing the location of host plants, crop rotation is one way to suppress potato beetle populations because it makes it harder for them to get to their food after they emerge in the spring. The problem is, the pest is rather mobile so long distances are needed between last year’s fields of potatoes and this year’s in order to have much of an effect. A few hundred feet doesn’t do much; a few thousand feet may help; but a mile or two is better. Physical barriers like rivers or roads in the terrain between rotated fields can enhance the effectiveness of crop rotation. Mulching the potato crop with straw after an early-season hilling may also reduce the Colorado potato beetle’s ability to locate potato fields, and the mulch creates an environment that favors beetle predators.

Growers using this system note that the straw should be spread so it’s touching the potato plants, but only a light layer of straw mulch is needed. Another way to protect plants is to place lightweight floating row covers over them and then seal the edges, well before the beetles arrive. Plastic-lined trenches have been used to trap beetles as they head toward a field of potatoes in the spring. A plow or heavy disk can be used to form a shallow trench around a field or along the edge of a field by a hedgerow or previous potato field where new beetles are likely to come from. Then black plastic is placed in the trenches, sort of like an ‘upside down’ raised bed. Since the beetles can’t fly when they first emerge, they walk toward their food and fall into these shallow trenches. The dust keeps them from getting enough of a grip to get out, and as the black plastic gets hot the beetles get roasted. Flaming of the early-season adults is another practice that’s employed to roast beetles. As they start to colonize field a tractor-mounted or hand-held flamer can be used to create a very quick pass of intense heat directed at the plants while they are still small.

This needs to be done when weather conditions are right for the beetles to be active on top of the foliage. The potato plant can recover from this brief exposure to intense heat, but the beetles are injured, and fall to the ground, unable to recover. For more information on managing Colorado potato beetle, go to an Extension pest management guide, such as and click on potatoes. Also check out for information on alternative and organic controls. Published: May 2004 Questionable Companions Mainstay of Organic Pest Control Won't Deter Colorado Potato Beetles Questionable Companions: Mainstay of Organic Pest Control Won't Deter Colorado Potato Beetles by Tara Moreau I just completed my Master's degree at the Nova Scotia Agricultural College, where I devoted two years of research to one troublesome agricultural pest: the Colorado potato beetle. Working with the Organic Agriculture Centre of Canada (OACC), I evaluated organic controls for this insect on potatoes. The results, which came as a shock to me, will perhaps be a disappointment to gardeners who place a lot of faith in companion planting. I realized early on that the 10-striped, leaf-eating Colorado potato beetle (CPB) is no ordinary insect.

Its ability to develop resistance to nearly all pesticides used against it, and its global distribution, make it one of the most notorious agriculture pests in the world - and therefore one of the most popular pest species in scientific literature. My particular interest was in the commonly prescribed technique of companion planting. Many publications devoted to home gardening and organic crop production recommend planting non-host plants or aromatic herbs as a means of reducing insect attack. I was intrigued with the concept. Could the presence of a non-host plant actually work to repel the beetle from potato plants nearby? Is there an unseen level of communication between plants and insects that can be used by growers for a more natural means of pest control? One of the greatest challenges I encountered in testing companion plants was the lack of information about which companion plant varieties worked best, how many companion plants were required to have an effect, and how to arrange the companion plants within the potatoes. These were the questions I sought to answer. Delving into the available literature, I realized that companion planting was a controversial subject, with various scientific data supporting and refuting its effectiveness. One study with the CPB reported that adult beetles were less attracted to the odors of potato plants in intercropped systems than in monocropped systems.

The researchers speculated that potato plant odors were masked by the odors of non-host plants, and that the CPB's host-plant searching behavior was reduced in the presence of non-host plants. Other researchers demonstrated that CPB populations were lower in high- diversity plots than in lower-diversity plots. In order to determine which companion plants to evaluate, I reviewed magazines, books, and internet sources, choosing plants that were most commonly recommended and that could be grown in Atlantic Canada. In the end I selected five: Bush beans (Phaseolus vulgaris cv. Provider), flax (Linum usitatissimum cv. Natasja), horseradish (Armoracia rusticana), marigold (Tagetes patula cv. Bolero) and tansy (Tanacetum vulgare), shown at the right. I started the companion plants in a greenhouse in the early spring, in order to grow large plants to transplant into the potato plots. The next stage of the project was to learn how to grow potatoes. I had no previous experience, and was unaware of the work required, but I managed to get research plots set up. I compared beetle densities between companion planted potato plots and potato plots with no companion plants.

The results from the 2-year study were not what I expected. Analysis of the CPB populations revealed that there were more beetles in plots with flax, marigold, and horseradish than in plots with no companion plants. I couldn't believe it. Not only did these companion plants not decrease CPB densities - their presence near potatoes actually increased the number of beetles. (The plots with Bush beans and tansy showed no difference from the control plots.) I was surprised to learn that my results were not unprecedented in this field of study. In trials evaluating companion planting for roses, researchers demonstrated that the companion plants increased the incidence of Japanese beetle attack on roses. While doing this research I had the opportunity to speak with many people who had success with companion planting and believed strongly in its effectiveness. However, my overall conclusion was that successful companion planting depends largely on the insect pest and the companion plants selected. Using Bush beans, flax, horseradish, marigold, and tansy as organic pest controls for the Colorado potato beetle would not be recommended, and I think this study does raise concerns about using companion plants without first verifying their effect on target pests.

Tara Moreau would welcome comments or questions on this subject by email at t@lenouveaupauvre.net . This article was first published in Rural Delivery , Volume 29 #2, July/August 2004 Potato Pests and Diseases (National Gardening Association) Photo by TBGDN Potatoes can be bothered by a variety of pests and diseases. Here are the most common and what to do about them. Pests Damaging pests can work quickly in a potato patch. Stroll through the plot regularly looking for insects and the damage they cause. It's a lot easier to deal with a pest before it becomes a disaster. If you choose to use sprays or dusts to prevent or control a pest problem, read the directions and follow them carefully. Colorado Potato Beetle This pest is present and working in just about every state. Destroy any potato bugs you see and check the underside of leaves for their orange egg masses. Both the adults, which are yellowish with black stripes, and the larvae, which are dark red or orange with black spots, feed on potato foliage. Pick them off or spray Bacillus thuringiensis San Diego on the young larvae.

Bt 'San Diego' attacks only the potato beetle larvae and is harmless to beneficial insects, animals and humans. Flea Beetle Flea beetles are tiny, black or brown, and pesky. They chew small holes in plant leaves and can do serious damage fast if they attack young plants. To foil these pests, cover young plants with fabric row covers as soon as you set them out. Keep flea beetle populations low through crop rotation and by maintaining high soil organic matter. Aphid These tiny insects can transmit virus diseases. They suck juices from the leaves and stems of potato plants, injuring them badly. Insecticidal soap sprays are an effective control. Wireworm Wireworms are the larvae of the click beetle. They're a problem when potatoes are planted in a section of garden that was recently sodded. Fully grown wireworms are 1/2- to 1 1/2-inches long. They're slender, brownish or yellowish white and tunnel into plant roots and tubers, spoiling them.

If your soil is heavily infested, contact your extension service agent for advice on solving the problem, or try growing your potatoes in the "tower" fashion mentioned in our article "Planting Potatoes." Diseases You may have a disease problem in the potato patch one year and none at all the next. The weather plays a big part in the health of a potato crop. Moisture and temperature conditions may trigger certain diseases, which will spread rapidly through the potato rows. But there's no need to simply sit back and let the environment determine the fate of your crop. To protect your crop, rotate the potato plot each year. Plant healthy, certified seeds. If you have severe disease problems, consider using a standard potato dust or spray regularly throughout the season. These are chemical mixtures that prevent some diseases such as late blight. They thwart some pests, too, such as the Colorado potato beetle. If you use a potato dust or spray, read and follow the directions carefully. To be effective, most standard dusts must be applied to the potato foliage every 7 to 10 days, beginning when the plants emerge from the ground. If you have questions about diseases or pests, your local cooperative extension service agent can help you.

Here are brief descriptions of a few of the common potato diseases. The fungus that causes common scab lives in the soil for many years. It's not active, though, when the soil pH is below 5.4, so if you have a serious scab problem, take a soil pH test. You may want to lower the pH by not liming or adding wood ashes to the potato section of the garden. Early Blight Early blight injures foliage and reduces overall yields. Affected leaves develop small, dark brown spots that often grow in size, and which eventually kill the leaves. Gardens in central, southern and eastern states are most susceptible. Planting certified seed and mulching with hay can prevent this disease. Late Blight Late blight is caused by the downy mildew fungus -- Phytophthora infestans, which triggered the Irish crop failures of 1845 and 1846. You'll notice the disease first by water-soaked areas on the leaves that turn brown and black as the leaf dies. The disease strikes often during cool, wet weather and may spread rapidly if the weather warms up. Plants can die in a severe case, and potatoes can be seriously affected, especially in storage.

Plant certified seed and use a potato dust to guard against late blight. Mosaic Virus Aphids can spread mosaic viruses, which cause potato leaves to curl and appear almost two-toned (light and dark green). Mosaic occurs throughout the United States and cuts down on the harvest, but it won't kill the plants. ' Kennebec ' and ' Katahdin ' varieties have some resistance to certain kinds of mosaic. Other articles in this series:

Question: What plant does the Colorado beetle attack?
Answer: Potato